Semi-conductor device and method of making



Jan. 13, 1959 f Ill Filed.l May l0, 1954 W. A. ROOVERS ETAL vSEMI-CONDUCTOR DEVICE AND METHOD OF MAKING l 'Il' 5)/ Jar/5 Dan/e/Jay/Ageing, fx ec ulf" AGENT United States Patent ,SEMI-CONDUCTOR DEVICEAND METHOD F MAKING Application May 10, 1954, Serial No. 428,509 Claimspriority, application Netherlands May 13, 1953 7 Claims. (Cl. 317-236)Eindhoven, and Otto Louis This invention relates to an electrode systemcomprising a semi-conductive body secured to a support sealed in a glassenvelope, and, more particularly, to semiconductor devices such ascrystal diodesand transistors,

In such systems, the semi-conductive body is usually constituted by acrystal and will hereinafter be referred to as such. lIt is known toseal a` metal tube in the wall of an envelope and to secure the crystalsupport therein by means of soft solder. This construction iscomparatively large and costly. However, it has the advantage that thesoldering'joint may be established at .a'low temperature at which thecrystal is not adversely affected. In this case, `the support for thecrystal is comparatively thick, i. e., slightly larger than thecross-sectional `area of the crystal, so that it can thus be introducedinto the j tube. A-modication of this construction involves seal- 'ingof the crystal support directly in the glass envelope; hence, the`temperatures employed are considerably higher. The crystal, however, inthis case,\is secured to a materially thinner support, which is alsocomparatively -long in order to space the crystal as far from the sealofthe support as possible.

One object of the present invention is to provide a comparatively shortsupport for the crystal sealed directly in the glass envelope, thetemperature of the crystal during the sealing operation remainingnevertheless low.

FA further object of the inventionis a short crystal support having lowheat resistance, which may be advantageous with respect to thedevelopment of heat in the crystal in the case of high current strength.

According to the invention, a support sealed directly in a glassenvelope has a portion inside the envelope having at least one sectionwhich is thicker than the portion thereof sealedin the envelope. Such`a` portion,

"hereinafter'referred to 'as-the -thickened portion, mayhave `a largerdiameter-than the crystal. Such a thickened portion may belocated-directly-adjacent the crystal,` but` it `may beadvantageousincertain applications to sarrange 1the thickened 4portion -between thejoint of thekcrystal and the supportpandA the sealof-the support in theglass. It should be noted that although reference is made above toaglassen'velope, other insulating materials having a melting pointexceeding that ofsoft solder, i. e. a melting point of more than 250 C.,may be utilised.

According to a further aspect of the invention, which involves a methodof manufacturing suchv an electrode system, during the sealing of thesupport in the envelope the thickened portions of the support areclamped in metal pincers.

The invention will now be described with reference to the accompanyingdrawing in which:

Figs. 1, 3, 5 to 7, and 9 and l0 are longitudinal crosssectional viewsillustrating crystal diodes in accordance with the invention;

Figs. 2, 4 and 8 show the support with the crystal and the envelopeduring the sealing operation.

ICC.

Fig. 1 shows a crystal diode having an envelope 1 constituted, forexample, of glass. It comprises a semiconductive crystal 2, for example,germanium or silicon. This crystal is soldered to a support 3constituted `by a thin wire portion sealed in the envelope at 4 and by athickened portion 5, located between the seal 4 andthe crystal 2. On thebase of the crystal remote from its support 3 fis located a pointelectrode 6, which is secured to a support 7. The latter is sealed at Sin the envelope li.

The provision ofthe thickened portion 5 has `a number of advantagescompared with the known. construction in which the crystal is secured toa support which is thin throughout its length. During the fastening ofthe crystal 2 tothe thickened portion 5 of the support 3, which isusually carried out before the sealing operation of the support to theenvelope, the thickened portion may in this case be grasped with heatedpincers, so that the heat transfer to the support is improvedconsiderably over that of a thin wire. Further, the portion `5' has alarge radiating surface, so that the crystal remains cooler during thesealing operation of the support to the envelope at 4. Finally, thethickened `portion ensures a satisfactory dissipation `of any heat`developed in the crystal, which may be comparatively great during theso-called power treatment, which -is a `transient electric treatmentwith high current strength carried out after the diode has beencompleted.

The temperature of the crystal may be controlled much more carefullyduring the sealing operation, if the thickened portion is grasped `inmetal pincers ofthe kind shown in Fig. 2. The pincers or holding membershown in that gure are constituted by a copperrod 9` having a bore at`the upperend forming a tube lwhich may have saw cuts forming a fewpincers 10. Ihese pincers grip a thickened portion 11, to which 'the'crystal is secured. The rod 9 is slightly thinner at its `upper endthan the inner diameter of the envelope 1, in order to avoid? localcooling of the glass during the sealing operation. The lower end lits inthe envelopeand serves for centering the crystal. While thesupportisgripped by the pincers 9, the wire portion 3 thereof is sealedto theenvelope at 4.

The weight of the support section inside the envelope ofthe diodes showninFigs. 2 .and 3, wherein the thickcned portion is designated 11,`isflower than` that of the diodes shown Vin Fig. l, so that in generalthe former will have greater resistance to vibrations than the latter.

The support used in the diode shown in Fig. S has a thickened portion 12provided with cooling -vanes `11i.

During the sealing operation carried out at` 4, cool air may be blownthrough one of the ducts 14 of .a double tube 15 into the envelope, thisairbeing exhausted through the other duct. Instead of using air, usemay, of course, be made of a gas which will protect thecrystal. In theembodiment `shown in Fig. `6, the thickened portion 16 has the `'shapeof acircular `disc secured to the support near the seal 4. The crystal 2is soldered `to the end of the `thin support 3. If` the `thickenedportion 16 is `graspediin pincers during `thesealing operation, thetemperature ofthe crystal may be still lower thanwinV fthe constructionshown in Fig. 3. The construction shown in Fig. 6 has, moreover, agreater resistance to shocks, since the end vof the wire has a lowerweight.

The construction shown in Fig. 7 corresponds largely to that shown inFig. 6; however, the support has a second thickened portion below thecrystal, so that a satisfactory dissipation of the heat developed in`the crystal is obtained. A

Due to the satisfactory cooling of the crystal during the sealingoperation, a construction as shown in Figs. 8, 9 and l() may also beobtained. To the support 3 is welded a round nickel plate 19, to whichthe crystal 2 is soldered. In' the same manner as shown in Fig. 2, thesupport is gripped in pincers 9 and the glass of the envelope is heatedand melted down on the support. As soon as the glass bears on thesupport, as is shown in Fig. 8, the interior of the envelope isevacuated through a lduct 20, bored in the pincers 9; thus, the glass isurged strongly on the support in a radial direction', it is, moref over,sucked into the envelope in an axialdirection; Hence, the envelope (Fig.9) exhibits ya groove 21 in the outer surface around the seal of thecrystal support, while the envelope may also have an axial, sphericalrecess 22 around the entrance of the support into the bulb. This recessmay be adjacent the thickened portion of the support, as is shown inFig. 10.

The exhaust operation during the sealing provides an improvement in thejoint between the glass and the support, due to the pressure by whichthe glass is urged against the support. Thus, the sealing temperaturemay be lower. The external dimensions of the envelope are, moreover,decreased, since the glass is, so to speak, drawn in. To further improvethe joint between the support and the envelope, the support may bepreviously provided with an enamel layer. This enamel is preferablyprovided in the form of paste, after the crystal has been secured to thesupport; the support, the enamel and the envelope are then sealedtogether simultaneously. The enamel could be applied by melting prior tothe fasten ing of the crystal to the support, but in this case theenamel could be affected duringA the crystal etching. If the enamel isapplied by melting to the support after the crystal has been securedthereto, the crystal would be exposed twice to high temperatures.However, if the envelope is sealed to the paste, the crystal need beheated only.once. During the sealing operation, this paste will melt atleast partly together with the envelope and the support, but at thecooler portions of the support the paste may remain unmelted, which,however, is not objectionable. For the sake of simplicity, the drawingshows only diodes. However, all the constructions shown may be used fortransistors, if instead of using one point electrode 6, use is made oftwo or more of these electrodes, arranged each on asupport 7 sealed inthe envelope.

The thickened portion of the support may be provided in various ways. Athicker rod may be welded to the support, as is shown in Fig. l; as analternative, a nail head may be clenched on the support (Figs. 2, 3 and7). Further, provision may be made of cooling vanes (Figs. 4 and 5), andas afurther alternative, a plate may be secured by welding'(Figs. 8 to10). Variants of this construction are, of course, possible.

2. An electrode system comprising an all-glass envelope, a first metallead sealed in one end of said envelope, a second metal lead sealed inthe other end of said envelope, said rst lead having a portion withinthe envelope of greater diameterthan the portion thereof sealed to theenvelope, a semi-conductive member having a diameter -less than that ofsaid portion of greater diameter and mounted `on said rst lead andwithin the envelope, an electrode secured to said second lead andcoupled to said semi-conductive member, and cooling means associatedwith said first lead.

,3., A method of manufacturing an electrode system comprising asemi-conductive body mounted on a metal lead having a portion of greaterdiameter than the remainder of said lead, which comprises the stepsof inserting said lead within a cylindrical glass body so that thesemi-conductive body and the portion of greater diameter are locatedbetween the ends of the glass body, grasping said portion of greaterdiameter with metal pincers inserted at one end of said glass body,thereafter heating the other end of said glass body to seal the same tothe metal lead beyond the portion of greater diameter while the latteris held by the pincers, thereafter removingv the pincers, and thereaftersealing another conductive lead to said one end of said glass body.

. 4. A semi-conductor device comprising an insulating envelope, asemi-conductive body, a support member While we have described ourinvention in connection with specific embodiments and applications,other modications thereof will be readily apparent to those skilled inthis art without departing from the spirit and scope of the invention asdefined in the appended claims.

What is claimed is:

1. A method of manufacturing an electrode system comprising asemi-conductive crystal secured to a support sealed in a glass envelopeand having a thicker portion within the envelope, comprising applyingenamel paste to the support, and sealing the support to the envelopewhile the thicker portion is grasped with metal pincers.

sealed in said envelope and supporting said semi-con` ductive bodytherewithm, said support member having, located inside the envelope, atleast one portion that is thicker than the portion of said member sealedin the envelope, and cooling vanes Aon said thicker portion.

5. A device as set forth in claim 4 wherein the thicker portion of thesupport member has a larger diameter than that of the semi-conductivebody.

6. A method of manufacturing a semi-conductor de vice comprising asemi-conductive body secured to a support member having a thickerportion adjacent the body than that portion sealed in a glass envelope,said thicker portion having a diameter exceeding that of thesemi-conductive body, which comprises the steps of grasping the thickerportion of said support with a heatconductive member, thereafter sealingthe support member into the glass envelope, and thereafter removing theheat-conductive member.

7. A method as set forth in claim 6 wherein the interior of the envelopeis exhausted during the sealing operation to provide a tighter seal tothe support member.

References Cited in the le of this patent UNITED STATES PATENTS 765,676,Midgley Apr. 5, 1904 817,664 Plecher Apr. 10, 1906 2,682,022 Doran June22, 1954 2,693,555 North et al. Nov. 2, 1954 2,697,805 Collins Dec. 2l,1954 2,697,806 Gates Dec. 21, 1954 j FOREIGN PATENTS 696,896 GreatBritain Sept. 9, 1953 696,904 Great Britain Sept. 9, 1953

